Currently, various small and thin LC devices suitable for, for example, portable communication terminals have been proposed. For example, Patent Documents 1 and 2 (identified below) describe one in which, by using a thin-film process, an inductor and a capacitor are formed, and these are integrally formed in a single element.
Patent Document 3 (identified below) describes one including an inductor and a capacitor inside a multilayer board. In the LC device described in Patent Document 3, the inductor is realized by a conductor pattern formed inside the multilayer board, and the capacitor is a mounting-type capacitor built in the multi-layer board.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 7-307440.
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2007-288104.
Patent Document 3: International Publication No. 2015-194373.
However, when the thin-film process is used as described in Patent Documents 1 and 2, the direct-current resistance of the inductor is increased, this inductor is not suitable to be used for large current applications, and the Q value is reduced.
In addition, since, in the structure described in Patent Document 3, the capacitor is disposed in an opening of the spiral-shaped inductor and the whole of these is covered by an insulating resin, the magnetic field that is generated at the inductor acts on the capacitor, thereby resulting in inductor loss. This reduces the Q value of the inductor.